[TagesschauIE] Add extractor for tagesschau.de (fixes #3049)

youtube_dl/extractor/__init__.py

@@ -266,6 +266,7 @@ from .streamcz import StreamCZIE
 from .swrmediathek import SWRMediathekIE
 from .syfy import SyfyIE
 from .sztvhu import SztvHuIE
+from .tagesschau import TagesschauIE
 from .teamcoco import TeamcocoIE
 from .techtalks import TechTalksIE
 from .ted import TEDIE